Internal combustion engine



FIG. 1 is a front elevational view of internal combustion engine showing our new design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a right side elevational view thereof; and,

FIG. 6 is a left side elevational view thereof.

The broken lines shown in FIGS. 2, 4, 5 and 6 are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for an internal combustion engine, as shown and described. 